Re: high overhead of functions blkg_*stats_* in bfq
From: Paolo Valente <hidden>
Date: 2017-11-06 16:11:44
Il giorno 06 nov 2017, alle ore 16:47, Paolo Valente =
[off-list ref] ha scritto:
=20quoted
=20 Il giorno 06 nov 2017, alle ore 16:00, Tejun Heo [off-list ref] ha =
scritto:
quoted
=20 Hello, =20 On Sun, Nov 05, 2017 at 07:21:01PM -0700, Jens Axboe wrote:quoted
It's pointless to give up on this so soon, when no effort has =
apparently
quoted
quoted
been dedicated to figuring out what the actual issue is yet. So no, =
no
quoted
quoted
patch that will just disable the stats is going to be accepted. =20 That said, I have no idea who uses these stats. Surely someone can answer that question. Tejun?=20 Except for the basic bytes / ios counts, it's all debug fluff, which should have been hidden behind a debug boot param or go under =
debugfs.
quoted
I'm not sure we can get rid of them at this point for cfq but I don't see why we'd have them for bfq. =20=20 Ok, then I think this is the right time to ask you what I can throw way for bfq. According to your documentation, basic non-debug stats should be: =20 blkio.time blkio.time_recursive blkio.sectors blkio.io_service_bytes blkio.io_service_bytes_recursive blkio.io_serviced blkio.io_serviced_recursive blkio.io_service_time blkio.io_service_time_recursive blkio.io_wait_time blkio.io_wait_time_recursive blkio.io_merged blkio.io_merged_recursive blkio.io_queued blkio.io_queued_recursive =20 So, I have to keep them in bfq, right? Or is there something I can remove for bfq, in your opinion? Of course, I would be very happy to =
remove stuff!
=20
Or, more mildly, could some of these stats be moved behind CONFIG_DEBUG_BLK_CGROUP? Thanks, Paolo
On the other end, here are the debugging stats I have borrowed from cfq: =20 blkio.avg_queue_size blkio.dequeue blkio.empty_time blkio.group_wait_time blkio.idle_time blkio.io_wait_time blkio.io_wait_time_recursive =20 These will be hidden behind the CONFIG_DEBUG_BLK_CGROUP option by one =
of the patches we are about to submit. Or do you want me to remove these = debugging stats completely? ok for me, just, if these parameters are = removed, then I guess the documentation of cgroups-v1 will have to be = somehow updated once the interface of bfq and cfq is unified.
=20 Thanks, Paolo =20quoted
Thanks. =20 --=20 tejun